Due to studies of Moving Picture Experts Group (MPEG) of International Organization for Standardization (ISO/IEC) and Video Coding Experts Group (VCEG) of International Telecommunication Union Telecommunication Standardization Sector (ITU-T) as organizations for standardization for video compression, a number of standards such as H.261, H.263, H.264, MPEG-1, MPEG-2, and MPEG-4 have been developed. Even though a slight difference may exist, the standards have structures including an estimation and compensation of movement, transform encoding, quantization, entropy coding, and in-loop filtering.
In particular, each standard may use various block sizes associated with a transform encoding, and, usually, a discrete cosine transform (DCT) scheme is commonly adopted and used.
Generally, DCT uses a block, including a pixel value of a differential image, as an input, and a performance of DCT is known to be better as a correlation between pixel values inside of the block becomes greater.
However, since the existing video compression standardization unconditionally performs the transform encoding and a frequency domain quantization with respect to a differential image block obtained after performing a movement prediction, when a boundary domain is included inside of the differential image block, an amount of transforms to be processed is so large that a compression efficiency may decrease.
Accordingly, a new encoding scheme may be required so that the compression efficiency may not decrease even when the boundary domain is included inside of the differential image block.